php生成验证码-原理版

最新推荐文章于 2021-04-01 00:32:09 发布

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<?php
error_reporting(E_ALL);
session_start();
define ("DIR_ROOT",dirname(__FILE__)."/lib/");

$data = array
    (
        2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g','h','i','j','k','m','n','p',
        'q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G',
        'H','I','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z'
    );

$keys = array_rand($data,4);
$code_str = $data[$keys[0]].$data[$keys[1]].$data[$keys[2]].$data[$keys[3]];
$_SESSION["code"] = $code_str;

$img_w        = 100;    //验证码图片的高度
$img_h        = 30;    //验证码图片的宽度
$font_size    = 15;    //文字的大小
$font_path    = DIR_ROOT."jdst.ttf";    //加载字体的位置
$scale        = 5;     //文字放大倍数
$img        = imagecreatetruecolor($img_w,$img_h);    //新建一个真彩色图像
$fontcolor    = imagecolorallocate($img,255,255,255); //生成的字体颜色
$background    = imagefilledrectangle($img,0,0,$img_w,$img_h,$fontcolor);//填充画布
//文字基准点横坐标
$base_point_x = $img_w/7;

//文字基准点纵坐标
$base_point_y = $img_h/3;

$color = imagecolorallocate($img, mt_rand(0, 100), mt_rand(20, 120), mt_rand(50, 150));
for ($i = 0; $i < 4; ++$i) {
    $coords = imagettftext($img, $font_size, 0, $base_point_x, 21, $color,$font_path, mb_substr($code_str, $i, 1, 'utf-8'));
    $base_point_x = $coords[2] + 10 ;
}
//头信息
header("Cache-Control: no-cache, must-revalidate");
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Pragma: no-cache");
header("Cache-control: private");
header('Content-Type: image/png');
imagepng($img);        //以png格式输出图像
imagedestroy($img);    //销毁图像
?>